I feel your pain. Buy if you're shelling out money it's probably quicker just to head to the materials crafter just outside of Fort Ranik and make it for 200g + 5 wood.
If you're poor like me and trying to save money, go just outside of Lion's Arch and kill all the fire imps; they drop it (probably average 1.5 charcoal per run) and you can salvage it out of glowing hearts with an expert kit rarely. And hey, if you get bored the nearby ettins once dropped 4 golds & a purple in a single run for me.
And hey, there's the hybrid method; farm imps and while you're at it salvage all the bows/staves/axes then use that wood to make charcoal as well (I keep non-expert salvage kits on me for just that sort of thing...which makes my bank space hate me).